Enhancement of arbuscular mycorrhizal fungal status of an established ginger crop through a mycorrhizal onion companion crop

Mycorrhiza-free and mycorrhizal seedlings of onion were transplanted in the field along rows of previously established plants of ginger in order to evaluate the possibility of enhancing arbuscular mycorrhizal (AM) colonization of ginger via a companion crop. Arbuscular mycorrhizal fungal colonization of roots determined 138 days after transplanting of onion showed that roots of all plants were colonized by the fungi. However, the level of AM fungal colonization of onion roots was significantly higher if onion seedlings were colonized by the fungi prior to transplanting than if they were not. Dry matter yield of onion was more than tripled by AM fungal inoculation. The level of AM fungal colonization of ginger roots was significantly enhanced in the presence of a mycorrhizal companion onion, not in the presence of a non-mycorrhizal one. However, the yield of ginger was unaffected by the presence of onion irrespective of mycorrhizal status. Our data raise the possibility that the mycorrhizal status of an established plant may be enhanced through the introduction of a compatible companion crop well colonized by AM fungi.